Various medical procedures have been developed to address heart disorders. In particular, CRT can be used to improve the conduction pattern and sequence of the heart. CRT involves the use of an implantable medical device (IMD) that is surgically implanted within the patient's body. Leads from the IMD can be affixed at a desired location within the heart to effectuate synchronous atrial and/or ventricular contractions. Typically, the location of the leads (e.g., therapy site) is selected based upon the anatomy, and disease type, disease severity and/or location of the blockage. Electrical stimulation signals can be delivered to resynchronize the heart, thereby, improving cardiac performance.
Despite these advantages, several shortcomings exist that limit the usefulness of CRT. Hemodynamic response to CRT typically varies from patient to patient, ranging from very positive (e.g., improvement) to substantially negative (e.g., deterioration) based upon the stimulation sites chosen to apply CRT as hemodynamic response can vary based upon the stimulation site used to apply CRT and on the timing of impulses (atrial-ventricular and ventricular-ventricular) not just electrode location. Presently, heart failure patients receiving CRT will have three leads placed in their heart. One lead in their right ventricular chamber, another in their right atrial chamber, and then a third lead that goes in their coronary sinus down one of the cardiac main branches or in a left ventricle epicardial position. However, not all patients have branches in the preferred stimulation sites or “sweet spots”. Patients vary a lot in their anatomical size of veins, number of veins, location of veins, and tortuosity of veins. Therefore, getting a lead to the sweet spot can be very challenging. A clinician can spend hours upon hours trying to get it to the right pacing spot. Even with all this work, present studies show only two-thirds of these patients respond to the CRT therapy. This can be due to patients having ischemia of heart tissue which can change the activation sequence in their pacing. Therefore, after implantation one patient may receive a great benefit from the CRT and another having ischemia in a certain area may not receive this benefit.
Presently the existing techniques and/or procedures to determine whether a specific patient will derive an acute hemodynamic benefit from CRT, are unable to determine or validate that a specific stimulation site will produce a positive hemodynamic response from CRT. For example, in order to determine acute hemodynamic benefits from CRT, the patient typically must be screened prior to receiving the therapy and the actual stimulation site used to apply CRT would be validated for each patient. In another method, the day after surgery the clinician will take the patient to an AV optimization setting to look at the timing between the right atrial contraction and the right ventricular contraction. Then the clinician can program the implantable device to obtain the best possible cardiac output or ejection fracture by timing right ventricular contractions and left ventricular contractions making them either simultaneous or sequential delay to improve the cardiac output as much as possible. However, as above, if the patient has ischemia of the heart tissue, the hemodynamics of the heart can only be optimized so much.